The overall objective of this proposal is to understand the role of vitamine A glycolipids as intermediates in the biosynthesis of glycoproteins. The involvement of polyisoprenyl phosphate carriers in the synthesis of asparagine-linked carbohydrate chains of certain glycoproteins has been established. However, the biosynthesis of glycoproteins, where the oligosaccharides and peptide chains are linked by an O-glycosidic bond has different requirements than the N-glycosidic link. Our earlier investigations point to the formation of vitamin A glycolipids in rat liver following administration of labeled retinol and mannose. It was further shown that the glycosyl portion of the retino glycolipid could be transferred to protein acceptors of rat liver smooth endoplasmic reticulum. While the mode of action of the retinoids remains obscure, vitamin A deficiency is marked by cessation of growth and lowered synthesis of mucus secreting cells. The major biological function of vitamin A may be to act as an intermediate for the assembly of the oligosaccharide portion of specific membrane glycoproteins needed to keep the integrity of the cell-membrane, as the regulation and differentiation of cell growth may be the result of interaction of surface glycoproteins with other molecules. It is proposed to study formation of retinoglycolipids from mannose, xylose, N-acetyl glucosamine and higher oligosaccharides that occur naturally, as parts of the glycosyl chains of membrane glycoproteins. The glycolipid will be purified and characterized with respect to the three entities: vitamin A, phosphate and sugar, using methods such as GLC-mass-spectrometry. While dolichol-linked intermediates might only be involved in the N-glycosidic bond, the retinoglycolipids might serve as intermediates for O-glycosidically linked glycoproteins.